Really? Can't speak for France, but it's definity low, specially for a senior dev. USD 56 470,69 equals EUR 49 465,78 as of today. You still need to pay taxes and (compulsory) social insurance from that. IMHO this is low, in some (western) european countries that amount may is junior dev entry salary IMHO. But someone responsible for a project that big could easily start at EUR 90 000,- or more (~USD 100 000,-). At least this is my experience.
Experienced senior devs in German speaking countries I know, which know what they are talking about, don't consider to work for less than EUR 80 000,- gross per year, for some this is the lowest base line. Just recently talked to a friend about that who works for a middle sized (~200 people), not very well known software company in Germany.